Estrogen receptor beta--a new dimension in estrogen mechanism of action

Alteration in protein expression in estrogen receptor alpha-negative human breast cancer tissues indicates a malignant and metastatic phenotype

Ductal carcinoma in situ (DCIS) represents the earliest identifiable breast cancer lesion. Disruption of the myoepithelial cell layer and basement membrane is a prerequisite for DCIS to initiate invasion into the stroma. The majority of epithelial cells overlying a focally-disrupted myoepithelial cell layer are estrogen receptor-alpha negative (ER(-)); however, adjacent cells within the same duct confined by an intact myoepithelial cell layer express high levels of ER. These ER (+) and ER (-) cells were microdissected from the same ducts of breast cancer patients. Differential proteins expressed by ER(+) and ER(-) cells were identified using two-dimensional gel electrophoresis followed by mass spectrometry and Western blot analysis. ER(-) cells express lower levels of superoxide dismutase, RalA binding protein, galectin-1, uridine phosphorylase 2, cellular retinoic acid-binding protein 1, S100 calcium binding protein A11, and nucleoside diphosphate kinase A or non-metastasis protein 23-H1 (nm23-H1). The upregulated protein, Rho GDP-dissociation inhibitor 1 alpha, may induce chemotherapy resistance. The significant findings are that the microdissected ER(-) cells express 12.6 times less cellular retinoic acid-binding protein 1, a protein involved in cellular differentiation, and 4.1 times less nucleoside diphosphate kinase A or nm23-H1, a metastasis suppressor, and express fewer proteins than adjacent ER(+) cells. The collective role of the alterations of protein expression in ER(-) cells may be to promote a more malignant phenotype than adjacent ER(+) cells, including a decreased ability to undergo apoptosis and differentiation, and an increased potential to damage DNA, metastasize, and resist to chemotherapy.

Revisiting estrogen: efficacy and safety for postmenopausal bone health

The rapid decline in endogenous estrogen production that occurs during menopause is associated with significant bone loss and increased risk for fragility fracture. While hormone therapy (HT) is an effective means to re-establish endogenous estrogen levels and reduce the risk of future fracture, its use can be accompanied by undesirable side effects such as stroke and breast cancer. In this paper, we revisit the issue of whether HT can be both safe and effective for the prevention of postmenopausal bone loss by examining standard and alternative doses and formulations of HT. The aim of this paper is to continue the dialogue regarding the benefits and controversies of HT with the goal of encouraging the dissemination of-up-to date evidence that may influence how HT is viewed and prescribed.

Lasofoxifene: Evidence of its therapeutic value in osteoporosis

INTRODUCTION

Osteoporosis is a skeletal disorder characterized by compromised bone strength and increased risk of fracture. It is a common disorder in elderly subjects and represents a major public health problem, affecting up to 40% postmenopausal women and 15% of men. Among the several therapeutical interventions, hormone replacement therapy (HRT) was traditionally seen as the gold standard for preventing osteoporotic fractures in postmenopausal women, as well as for the management of menopausal symptoms. However HRT, especially if administered long-term, may lead to an increased risk of breast and, when unopposed by progestins, endometrial cancers. Alternative therapies include bisphosphonates and raloxifene, a selective estrogen receptor modulator (SERM). While the former have been associated with suboptimal adherence, the latter was considerably less potent than estrogen and its effect in the prevention of nonvertebral fractures remain uncertain.

AIMS

The purpose of this article is to review the clinical trials of lasofoxifene, a new SERM for the treatment of postmenopausal osteoporosis. The medical literature was reviewed for appropriate articles containing the terms "lasofoxifene" and SERMs".

EVIDENCE REVIEW

There are three (phase II or phase III) clinical trials that clearly demonstrate efficacy and safety of this new SERM in the suppression of bone loss and the prevention of vertebral and nonvertebral fractures. Moreover, lasofoxifene treatment also reduced breast cancer risk and the occurrence of vaginal atrophy.

PLACE IN THERAPY

With its increased potency and efficacy on the prevention of nonvertebral fractures lasofoxifene may be an alternative and cost-effective therapy for osteoporosis in postmenopausal women.

Subsite-specific differences of estrogen receptor beta expression in the normal colonic epithelium: implications for carcinogenesis and colorectal cancer epidemiology

OBJECTIVE

This study aimed at investigating whether a differential estrogen receptor beta (ER-beta) expression between the colonic subsites could correspond to a modification in proliferation, apoptosis, and adhesion of the normal colonocytes.

METHODS

ER-beta, Ki-67, Bcl-2, and E-cadherin expressions were investigated immunohistochemically, in normal epithelium biopsies from the ascending and the descending colon of 53 individuals, who underwent colonoscopy for the investigation of anemia and in whom no local pathology was identified.

RESULTS

ER-beta immunoreactivity has been shown to be stronger at the superficial epithelium than the crypts' base, the difference being important only for the ascending colon. In addition, ER-beta expression was higher in the superficial epithelium of the ascending colon than that of the descending colon. The variations of ER-beta expression did not correspond to the alterations in Ki-67, Bcl-2, and E-cadherin expression.

CONCLUSION

A subsite-specific variation of ER-beta expression has been shown in the normal colonic epithelium. This modulation of ER-beta might account for some well established specificities of colorectal cancer epidemiology like the right-sided predominance of the neoplasm in women and its gradual shift to more proximal sites over time.

Disposition of soy isoflavones in normal human breast tissue

BACKGROUND

Despite decades of research on the relation between soy and breast cancer, questions regarding the absorption, metabolism, and distribution of isoflavones in breast tissue largely remain unanswered.

OBJECTIVE

We evaluated the potential health effects of isoflavone consumption on normal breast tissue; isoflavone concentrations, metabolites, and biodistribution were investigated and compared with 17beta-estradiol exposure.

DESIGN

In this dietary intervention study, healthy women were randomly allocated to a soy milk (n = 11; 16.98-mg genistein and 5.40-mg daidzein aglycone equivalents per dose), soy supplement (n = 10; 5.27-mg genistein and 17.56-mg daidzein aglycone equivalents per dose), or control (n = 10) group. After a run-in period > or = 4 d, 3 doses of soy milk or soy supplements were taken daily for 5 d before an esthetic breast reduction. Blood and breast biopsies were collected during surgery and analyzed with liquid chromatography-tandem mass spectrometry.

RESULTS

After soy administration, genistein and total daidzein concentrations, which were expressed as aglycone equivalents, ranged from 135.1 to 2831 nmol/L and 105.1 to 1397 nmol/L, respectively, in hydrolyzed serum and from 92.33 to 493.8 pmol/g and 22.15 to 770.8 pmol/g, respectively, in hydrolyzed breast tissue. The major metabolites identified in nonhydrolyzed samples were genistein-7-O-glucuronide and daidzein-7-O-glucuronide, with an overall glucuronidation of 98%. Total isoflavones showed a breast adipose/glandular tissue distribution of 40:60, and their mean (+/-SEM) derived 17beta-estradiol equivalents toward estrogen receptor beta were 21 +/- 4-fold and 40 +/- 10-fold higher than the 17beta-estradiol concentrations in adipose (0.283 +/- 0.089 pmol/g, P < 0.001) and glandular (0.246 +/- 0.091 pmol/g, P = 0.001) fractions, respectively.

CONCLUSION

After intake of soy milk and soy supplements, isoflavones reach exposure levels in breast tissue at which potential health effects may occur.

Dietary-induced ERbeta upregulation counteracts intestinal neoplasia development in intact male ApcMin/+ mice

Most sporadic colorectal cancers (CRCs) develop through the adenoma-carcinoma sequence pathway and are initiated by adenomatous polyposis coli (APC) gene mutations. Estrogen receptor beta (ERbeta) is recognized to progressively reduce its expression in adenomatous and carcinomatous tissues in humans. Moreover, ERbeta deficiency enhances small intestinal tumorigenesis in rodents. In the Apc(Min/+) mouse model, we evaluated intestinal polyp development and ERbeta expression plus other biological parameters influencing tumor growth (epithelial cell proliferation, apoptosis and migration) following the addition of a combination of the ERbeta-selective agonist silymarin (SIL) and/or lignin (LIG) to a high-fat/low-fiber diet. Forty-five Apc(Min/+) mice were divided in four groups: animals fed on the tumorigenic high-fat/low-fiber diet, the tumorigenic diet supplemented with SIL (0.02%) or purified LIG (6.24%) or SIL (0.005%) + LIG (6.24%). In these animals, we assessed polyp number and volume and their degree of dysplasia together with ERbeta messenger RNA (mRNA) and protein levels and epithelial cell proliferation, migration and apoptosis. The latter group of parameters was evaluated in normal and adenomatous mucosa and the results compared with those found in wild-type (WT) mice fed on the control diet. The addition of SIL or LIG to the diet and even more the specific combination of the two significantly counteracted intestinal tumorigenesis and increased ERbeta mRNA and protein levels. Cell proliferation and apoptosis were rebalanced and cell migration accelerated, restoring values similar to those observed in WT animals. Our results further support a protective effect of ERbeta in CRC suggesting the use of the combination of SIL-LIG as a potential approach against CRC development.

Hormones in international meat production: biological, sociological and consumer issues

Beef and its products are an important source of nutrition in many human societies. Methods of production vary and include the use of hormonal compounds ('hormones') to increase growth and lean tissue with reduced fat deposition in cattle. The hormonal compounds are naturally occurring in animals or are synthetically produced xenobiotics and have oestrogenic (oestradiol-17beta and its esters; zeranol), androgenic (testosterone and esters; trenbolone acetate) or progestogenic (progesterone; melengestrol acetate) activity. The use of hormones as production aids is permitted in North American countries but is no longer allowed in the European Union (EU), which also prohibits the importation of beef and its products derived from hormone-treated cattle. These actions have resulted in a trade dispute between the two trading blocs. The major concern for EU authorities is the possibility of adverse effects on human consumers of residues of hormones and metabolites. Methods used to assess possible adverse effects are typical of those used by international agencies to assess acceptability of chemicals in human food. These include analysis of quantities present in the context of known biological activity and digestive, absorptive, post-absorptive and excretory processes. Particular considerations include the low quantities of hormonal compounds consumed in meat products and their relationships to endogenous production particularly in prepubertal children, enterohepatic inactivation, cellular receptor- and non-receptor-mediated effects and potential for interference with growth, development and physiological function in consumers. There is particular concern about the role of oestradiol-17beta as a carcinogen in certain tissues. Now subject to a 'permanent' EU ban, current evidence suggests that certain catechol metabolites may induce free-radical damage of DNA in cell and laboratory animal test systems. Classical oestrogen-receptor mediation is considered to stimulate proliferation in cells maintaining receptivity. Mathematical models describing quantitative relationships between consumption of small amounts of oestrogens in meat in addition to greater concentrations from endogenous production, chemical stoichiometry at cellular level and human pathology have not been developed. Such an approach will be necessary to establish 'molecular materiality' of the additional hormone intake as a component of relative risk assessment. The other hormones, although generally less well researched, are similarly subject to a range of tests to determine potentially adverse effects. The resulting limited international consensus relates to the application of the 'precautionary principle' and non-acceptance by the European Commission of the recommendations of the Codex Alimentarius Commission, which determined that meat from cattle, hormone-treated according to good practice, was safe for human consumers. The present review considers the hormone issue in the context of current international social methodology and regulation, recent advances in knowledge of biological activity of hormones and current status of science-based evaluation of food safety and risk for human consumers.

Enhanced ERbeta immunoexpression and apoptosis in the germ cells of cimetidine-treated rats

BACKGROUND

Cimetidine, refereed as antiandrogenic drug, causes hormonal changes in male patients such as increased testosterone and FSH levels. In the rat testis, structural alterations in the seminiferous tubules have been related to germ cell loss and Sertoli cell death by apoptosis. Regarding the important role of Sertoli cells in the conversion of testosterone into estrogen, via aromatase, the immunoexpression of estrogen receptors-beta (ERbeta) was evaluated in the germ cells of untreated and treated rats with cimetidine. A relationship between ERbeta immunoreactivity and apoptosis was also investigated in the germ cells of damaged tubules.

METHODS

Immunohistochemistry for detection of ERbeta and TUNEL method were performed in testicular sections of adult male rats treated with 50 mg/Kg of cimetidine (CmG) or saline solution (CG) for 52 days.

RESULTS

In CG, a cytoplasmic immunoexpression for ERbeta was observed in spermatogonia, primary spermatocytes and spermatids. An evident ERbeta immunoreactivity was always observed in the flagellum and residual bodies of late spermatids. In CmG, the cytoplasm or cytoplasm and nuclei of germ cells of the damaged tubules by cimetidine showed enhanced ERbeta immunostaining. TUNEL-labeling was usually observed in the same germ cell types exhibiting enhanced ERbeta immunoreactivity.

CONCLUSION

The presence of ERbeta immunolabeling in the flagellum and residual bodies of spermatids reinforces the role of estrogen in spermiogenesis. The overexpression of ERbeta in the germ cells of CmG could be related to a possible interference of cimetidine on tubular androgenization and/or on the intratubular aromatase due to Sertoli cell damage. The parallelism between ERbeta overexpression and apoptosis indicates a participation of ERbeta on germ cell death.

The effect of genistein aglycone on cancer and cancer risk: a review of in vitro, preclinical, and clinical studies

In Asian epidemiological studies, health benefits, including reduced incidence of breast and prostate cancers, are attributed to soy food and isoflavone consumption. The recent increased intake of soy foods and supplements in the American diet has raised concerns about the possible estrogen-like effects of natural isoflavones and possible promotion or propagation of estrogen-sensitive cancers. These concerns are primarily based on in vitro and rodent data which suggest that genistein aglycone can stimulate tumor cell proliferation and growth in mice having deficient immune systems. In contrast, a recent nested case-control study and meta-analysis of numerous epidemiological studies show an inverse correlation between genistein intake and breast cancer risk. Furthermore, clinical studies in osteopenic and osteoporotic, postmenopausal women support the breast and uterine safety of purified naturally derived genistein administered for up to 3 years. In this review, we summarize the in vitro, preclinical and clinical evidence for the safety of natural genistein.

Novel female sex-dependent actions of oestrogen in the intestine

The intestine is an oestrogen responsive organ and circulatory oestrogens suppress Cl(-) secretion across the epithelium of the colon to promote fluid retention at the luteal stage of the menstrual cycle. Ion transporters in the colon which are involved in Cl(-) secretion show differential expression between males and females as do the signalling protein kinase intermediates involved in acutely regulating these transporters. Work from our laboratory has identified the KCNQ1/KCNE3 channel as one of the principal targets for oestrogen-induced signalling cascades in the distal colon. Through inhibition of the KCNQ1 channel, basolateral K(+) recycling is decreased so reducing the favourable electrochemical gradient for Cl(-) extrusion at the apical membrane. The actions of oestrogen on non-reproductive tissues such as the colon, kidney, lung and sweat gland will affect whole body electrolyte and fluid homeostasis and also have consequences for reproductive potential.

Estrogen Receptor βΔ6 (ERβΔ6) Isoform in Human Endometrial Hyperplasia and Adenocarcinoma

Estrogen receptor (ER)-beta may play a significant role in estrogen action in several human tissues. Estrogen receptor beta may act as a transdominant repressor of ER alpha transcriptional activity trough heterodimers form. Estrogen receptor messenger RNA (mRNA) variants also may be involved in various diseases, including endometrial cancer. The absence of estrogen receptors has often correlated with poor prognosis of endometrial tumors. The objective of the study was to determine the number of mRNA ER beta delta 6 and (wtER beta) in 1 microgram total RNA obtained from tissues of normal, hyperplastic endometrium, and endometrial adenocarcinoma. This study was designed to evaluate possible differences in the ER beta delta 6 and wtER beta messenger RNA (mRNA) level in the normal, hyperplastic endometrium, and endometrial endometrioid adenocarcinoma (G1, G2 morphological degree). Adenocarcinoma showed significantly lower ER beta delta 6 mRNA level than proliferative (p = 0.032) and secretory (p = 0.01) endometrium. A decrease of mRNA wtER beta in endometrial adenocarcinoma (p = 0.006) also was observed.

Vertebrate sex steroid receptors: evolution, ligands, and neurodistribution

This review focuses on our current understanding of vertebrate sex steroid receptors, with an emphasis on their evolutionary relationships. These relationships are discussed based on nucleotide and amino acid sequence data, which provide clues to the process by which structure-function relations have originated, evolved, and been maintained over time. The importance of the distribution of sex steroid receptors in the vertebrate brain is discussed using the example of androgen receptor sites and their relatively conserved localizations in the vertebrate brain.

Breast cancer, estrogen receptor and ligands

This review emphasizes the relationship of breast cancer, estrogen receptor and ligands, especially the centrality of the estrogen receptor, which mediates on one hand the hormone-induced gene transcription and on the other hand the anti-estrogen action against breast cancer. The characterization of the estrogen receptor ligand-binding domain co-crystallized with agonists or antagonists provided a molecular basis to gain an insight into the regulation of estrogen receptor and, thereby, to describe the mechanism of the hormone therapy in treating breast cancer.

Estrogen receptor beta as a mitochondrial vulnerability factor

We recently demonstrated mitochondrial localization of estrogen receptor beta (ERbeta). We herein confirm the mitochondrial localization of ERbeta by the loss of mitochondrial ERbeta immunoreactivity in ERbeta knockdown cells. A phenotype change characterized as an increase in resistance to oxidative stressors is associated with ERbeta knockdown. ERbeta knockdown results in a lower resting mitochondrial membrane potential (Deltapsim) and increase in resistance to hydrogen peroxide-induced Deltapsim depolarization in both immortal hippocampal cells and primary hippocampal neurons. ERbeta knockdown cells maintained ATP concentrations despite insults that compromise ATP production and produce less mitochondrial superoxide under oxidative stress. Furthermore, similar mitochondrial phenotype changes were identified in primary hippocampal neurons derived from ERbeta knock-out mice. These data demonstrate that ERbeta is expressed in mitochondria and function as a mitochondrial vulnerability factor involved in Deltapsim maintenance, potentially through a mitochondrial transcription dependent mechanism.

Bioactivity-based screening of antibiotics and hormones

Bioactivity-based screening methods are relatively cheap, quick and easy to use tools. Especially with respect to antimicrobial residues and compounds with hormonal activity, they form a very cost-effective alternative to physical chemical methods in large-scale surveillance and monitoring programs, where their main purpose is to identify samples that require additional chemical confirmation. A major advantage is their intrinsic capability to detect unknown compounds and new hazards. This review shows an overview of the available methods and their potential and limitations for regulatory control.

Estrogen receptor subtype beta2 is involved in neuromast development in zebrafish (Danio rerio) larvae

Estrogens are known to play a role in both reproductive and non-reproductive functions in mammals. Estrogens and their receptors are involved in the development of the central nervous system (brain development, neuronal survival and differentiation) as well as in the development of the peripheral nervous system (sensory-motor behaviors). In order to decipher possible functions of estrogens in early development of the zebrafish sensory system, we investigated the role of estrogen receptor beta(2) (ERbeta(2)) by using a morpholino (MO) approach blocking erbeta(2) RNA translation. We further investigated the development of lateral line organs by cell-specific labeling, which revealed a disrupted development of neuromasts in morphants. The supporting cells developed and migrated normally. Sensory hair cells, however, were absent in morphants' neuromasts. Microarray analysis and subsequent in situ hybridizations indicated an aberrant activation of the Notch signaling pathway in ERbeta(2) morphants. We conclude that signaling via ERbeta(2) is essential for hair cell development and may involve an interaction with the Notch signaling pathway during cell fate decision in the neuromast maturation process.

Identification of xenoestrogens in food additives by an integrated in silico and in vitro approach

In the search for xenoestrogens within food additives, we have analyzed the Joint FAO-WHO expert committee database, containing 1500 compounds, using an integrated in silico and in vitro approach. This analysis identified 31 potential estrogen receptor alpha ligands that were reduced to 13 upon applying a stringent filter based on ligand volume and binding mode. Among the 13 potential xenoestrogens, four were already known to exhibit an estrogenic activity, and the other nine were assayed in vitro, determining the binding affinity to the receptor and biological effects. Propyl gallate was found to act as an antagonist, and 4-hexylresorcinol was found to act as a potent transactivator; both ligands were active at nanomolar concentrations, as predicted by the in silico analysis. Some caution should be issued for the use of propyl gallate and 4-hexylresorcinol as food additives.

Bazedoxifene for the prevention of postmenopausal osteoporosis

Bazedoxifene acetate is a novel, chemically distinct selective estrogen receptor modulator (SERM) that has been specifically developed after a stringent preclinical screening in order to obtain favorable effects on the skeleton and lipid metabolism with the additional improvement of a neutral effect on hot flushes and without stimulating the uterus or the breast. In both preclinical and clinical studies this SERM was shown to maintain BMD, prevent fractures, and reduce total cholesterol. Moreover, bazedoxifene also showed an improved uterine profile and demonstrated estrogen antagonistic activity on the endometrium. Importantly, this latter capacity has led to the development of a novel class of menopausal therapy called tissue selective estrogen complex (TSEC), in which bazedoxifene is combined with conjugated estrogen. The rationale for selecting bazedoxifene as the SERM in this TSEC combination is that it may offset estrogen stimulation of endometrial and breast tissue, without the necessity of using a progestin in women with an intact uterus, without aggravating menopausal vasomotor symptoms, but with an additive effect on bone. Preliminary data from phase 3 clinical trials appear to confirm this hypothesis, showing a greater effect of bazedoxifene on BMD with respect to raloxifene, coupled with efficacy on menopausal vasomotor symptoms not achieved by SERM alone. These properties and the safety profile of this combination, if confirmed long-term in ongoing phase 3 trials, might significantly affect the way women and physicians approach menopause and its related disorders.

The F-domain of estrogen receptor-alpha inhibits ligand induced receptor dimerization

The role of the carboxyl terminal F-domain of estrogen receptor (ERalpha) is uncertain, but evidence suggests that this region may impart internal restraint on ER dimerization in the presence of 17beta-estradiol (E2). To identify the C-terminal residues affecting human ERalpha activation, we created a series of deletions and examined E2 induced receptor dimerization and transactivation. Deletion of the final 24 C-terminal amino acids of the F-domain (Delta7b) yielded a fivefold increase in dimerization, when compared to wild type (wt) ERalpha in the presence of 2nM E2, utilizing a yeast two-hybrid assay. This increase in dimerization is similar to that observed when the entire F-domain was deleted. Measurement of mutant:mutant homodimer formation yielded similar increases compared to mutant:wt interactions. Interestingly, a point mutation at the C-terminus (mut 3) showed increases in dimerization comparable to that of Delta7b in the presence of nanomolar amounts of E2. However, at sub-nanomolar levels of E2, mut 3 behaved similarly to wt ERalpha, whereas Delta7b maintained striking increases in dimerization. Determination of E2 binding affinity (Kd) constants revealed only marginal differences for wt and F-domain mutants, suggesting that the F-domain affects dimerization directly. We also observed enhanced interaction of F domain mutants with p160 family coactivator SRC1. Finally, transcriptional regulation of estrogen responsive reporters, 2XERE-LacZ and 3XERE-Luc in yeast and mammalian cells, respectively, reflected the increased propensity for dimerization by F domain mutants. Together, these data indicate that the C-terminal amino acids of ERalpha are critical for attenuation of E2 induced receptor dimerization and transcriptional activity.

Differential regulation of the inducible nitric oxide synthase gene by estrogen receptors 1 and 2

Estrogen has both rapid and longer term direct effects on cardiovascular tissues mediated by the two estrogen receptors, ESR1 and ESR2. Previous work identified that estrogen regulates the expression of inducible nitric oxide synthase (NOS2A) in vascular smooth muscle cells (VSMC). ESR2 knockout mice have vascular dysfunction due to dysregulation of NOS2A expression and these mice are hypertensive (Zhu et al. Science 2002 295 505-508). Here, we report studies to examine the differential regulation of NOS2A gene expression by ESR1 and 2. Immunoblotting and RT-PCR studies revealed that different VSMC lines expressed different levels of ESR1 and ESR2 protein and mRNA. VSMC from different vascular beds were studied, including aortic VSMC expressing ESR1 and radial (Rad) VSMC expressing ESR2. E(2) inhibited NO production and NOS2A protein expression in aortic VSMC. Human NOS2A promoter-reporter studies revealed suppression of NOS2A reporter activity by E(2) in aortic VSMC, and stimulation of NOS2A reporter activity by E(2) in Rad arterial VSMC. In heterologous expression studies of COS-7 cells lacking endogenous ER, E(2) treatment of COS-7 cells did not alter NOS2A reporter activity in the presence of ESR1, while reporter activity increased 2.3-fold in the presence of ESR2. Similar experiments in COS-7 cells using the selective estrogen receptor modulator raloxifene showed that raloxifene caused a reduction in NOS2A reporter activity with ESR1 coexpression and an increase with ESR2 coexpression. Rat VSMC expressing ESR2 but not ESR1 also showed increased NOS2A reporter activity with E(2) treatment, an effect lost when ESR1 was introduced into the cells. Taken together, these data support that hNOS2A transcription is regulated positively by ESR2 and negatively by ESR1 in VSMC, supporting differential actions of these two estrogen receptors on a physiologically relevant gene in VSMC.

Estrogen regulation of glucose metabolism and mitochondrial function: therapeutic implications for prevention of Alzheimer's disease

Estrogen-induced signaling pathways in hippocampal and cortical neurons converge upon the mitochondria to enhance mitochondrial function and to sustain aerobic glycolysis and citric acid cycle-driven oxidative phosphorylation and ATP generation. Data derived from experimental and clinical paradigms investigating estrogen intervention in healthy systems and prior to neurodegenerative insult indicate enhanced neural defense and survival through maintenance of calcium homeostasis, enhanced glycolysis coupled to the citric acid cycle (aerobic glycolysis), sustained and enhanced mitochondrial function, protection against free radical damage, efficient cholesterol trafficking and beta amyloid clearance. The convergence of E(2) mechanisms of action onto mitochondrial is also a potential point of vulnerability when activated in a degenerating neural system and could exacerbate the degenerative processes through increased load on dysregulated calcium homeostasis. The data indicate that as the continuum of neurological health progresses from healthy to unhealthy so too do the benefits of estrogen or hormone therapy. If neurons are healthy at the time of estrogen exposure, their response to estrogen is beneficial for both neuronal survival and neurological function. In contrast, if neurological health is compromised, estrogen exposure over time exacerbates neurological demise. The healthy cell bias of estrogen action hypothesis provides a lens through which to assess the disparities in outcomes across the basic to clinical domains of scientific inquiry and on which to predict future applications of estrogen and hormone therapeutic interventions sustain neurological health and to prevent age-associated neurodegenerative diseases such as Alzheimer's. Overall, E(2) promotes the energetic capacity of brain mitochondria by maximizing aerobic glycolysis (oxidative phosphorylation coupled to pyruvate metabolism). The enhanced aerobic glycolysis in the aging brain would be predicted to prevent conversion of the brain to using alternative sources of fuel such as the ketone body pathway characteristic of Alzheimer's.

Estrogen actions on mitochondria--physiological and pathological implications

Estrogens are potent neuroprotective hormones and mitochondria are the site of cellular life-death decisions. As such, it is not surprising that we and others have shown that estrogens have remarkable effects on mitochondrial function. Herein we provide evidence for a primary effect of estrogens on mitochondrial function, achieved in part by the import of estrogen receptor beta (ERbeta) into the mitochondria where it mediates a number of estrogen actions on this vital organelle. ERbeta is imported into the mitochondria, through tethering to cytosolic chaperone protein and/or through direct interaction with mitochondrial import proteins. In the mitochondria, ERbeta can affect transcription of critical mitochondrial genes through the interaction with estrogen response elements (ERE) or through protein-protein interactions with mitochondrially imported transcription factors. The potent effects of estrogens on mitochondrial function, particularly during mitochondrial stress, argues for a role of estrogens in the treatment of mitochondrial defects in chronic neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) and more acute conditions of mitochondrial compromise, like cerebral ischemia and traumatic brain injury.

Immunolocalisation of oestrogen receptors alpha (ERalpha) and beta (ERbeta) in porcine embryos and fetuses at different stages of gestation

The sites of oestrogen action can be shown by the localisation of their receptors in the target tissues. The aim of the present study was to show the localisation of oestrogen receptors in porcine embryos and fetuses obtained on days 18, 22, 32, 40, 50, 60, 71 and 90 post coitum (p.c.). The visualisation of proteins was conducted in embryos and various fetal organs such as gonads, uterus, lung, kidney, intestine and adrenal gland. Both ERs were observed in the blastocysts on day 18 p.c. In the male, ERbeta was detected in the testis and epididymis, whereas ERalpha was present in the efferent ductules. In the female, ERbeta was detected in the ovarian stromal cells investing the oocyte nests, while ERalpha protein was detected in the surface epithelium. In the uterus, ERs were present in the stromal cells, while ERbeta was present in the luminal epithelium. In the non-reproductive fetal porcine tissues ERbeta was localised in the lungs, kidneys, adrenal glands and in the umbilical cords. Both ERs were observed in the intestine. It is possible that ERbeta may play important roles in the development of the adrenal gland, testis, kidney and lungs, while both ERs are involved in the development of the ovary, uterus, epididymis and intestine of the porcine fetus.

Roles of oestrogen receptors alpha and beta in behavioural neuroendocrinology: beyond Yin/Yang

Oestrogen receptor beta (ERbeta) was discovered more than 10 years ago. It is widely distributed in the brain. In some areas, such as the entorhinal cortex, it is present as the only ER, whereas in other regions, such as the bed nucleus of the stria terminalis and preoptic area, it can be found co-expressed with ERalpha, often within the same neurones. These ERs share ligands, and there are several complex relationships between the two receptors. Initially, the relationship between them was labelled as 'yin/yang', meaning that the actions of each complemented those of the other, but now, years later, other relationships have been described. Based on evidence from neuroendocrine and behavioural studies, three types of interactions between the two oestrogen receptors are described in this review. The first relationship is antagonistic; this is evident from studies on the role of oestrogen in spatial learning. When oestradiol is given in a high, chronic dose, spatial learning is impaired. This action of oestradiol requires ERalpha, and when ERbeta is not functional, lower doses of oestradiol have this negative effect on behaviour. The second relationship between the two receptors is one that is synergistic, and this is illustrated in the combined effects of the two receptors on the production of the neuropeptide oxytocin and its receptor. The third relationship is sequential; separate actions of the two receptors are postulated in activation and organisation of sexually dimorphic reproductive behaviours. Future studies on all of these topics will inform us about how ER selective ligands might affect oestrogen functions at the organismal level.

In utero and postnatal exposure to a phytoestrogen-enriched diet increases parameters of acute inflammation in a rat model of TNBS-induced colitis

Inflammatory bowel disease (IBD) is very common in Europe and USA. Its incidence in East Asia has been traditionally low, albeit the risk of IBD increases in Asian immigrants adopting western lifestyles, suggesting a strong role of environmental/dietary factors in IBD. A lifelong exposure to phytoestrogen-rich diets has been associated with a decreased risk of developing breast cancer and might also be protective against IBD. We studied the influence of in utero and postnatal exposure to a phytoestrogen (PE)-rich diet on acute inflammation in an animal model of TNBS-induced colitis. Wistar rats were exposed in utero and postnatally to high (genistein: 240 microg/g feed; daidzein: 232 microg/g feed) or very low levels (genistein and daidzein <10 microg/g feed) of phytoestrogen isoflavones fed to pregnant dams with the diet and throughout nursing. After weaning, the offspring had free access to these diets. At the age of 11 weeks, colitis was induced with an enema of TNBS. After 3 days, animals were sacrificed and tissues were collected for histological evaluation and analysis of molecular markers of inflammation. Animals kept on a PE-rich diet (PRD) had higher colon weights than animals on low PE-levels (PDD), suggesting enhanced acute inflammation by phytoestrogens. This result was supported by histological findings and by analysis of myeloperoxidase activity. Interestingly, relative mRNA and protein expression of cyclooxygenase-2 (COX-2) were modulated in rats on PRD, providing evidence that COX-2, the inducible isoform of the enzyme, is involved in the management of colonic inflammation. Our results suggest that early-in-life exposure to PE might not protect against the development of IBD but enhances the extent of acute inflammation.

Estrogen induces rapid translocation of estrogen receptor beta, but not estrogen receptor alpha, to the neuronal plasma membrane

Estrogen receptors can activate transcription in the nucleus, and activate rapid signal transduction cascades in the cytosol. Multiple reports identify estrogen receptors at the plasma membrane, while others document the dynamic responses of estrogen receptor to ligand binding. However, the function and identity of membrane estrogen receptors remain controversial. We have used confocal microscopy and cell fractionation on the murine hippocampus-derived HT22 cell line and rat primary cortical neurons transfected with estrogen receptor-green fluorescent protein constructs to address the membrane localization of these receptors. We observe translocation of estrogen receptor beta (beta) to the plasma membrane 5 min after exposure to 17beta-estradiol, whereas estrogen receptor alpha (alpha) localization remains unchanged. Membrane localization of estrogen receptor beta is transient, selective for 17beta-estradiol, and is not blocked by ICI182,780. Inhibition of the mitogen-activated protein kinase pathway does not block estrogen-mediated estrogen receptor beta membrane translocation, and in fact prolongs membrane localization. These data suggest that while both estrogen receptor alpha and estrogen receptor beta can be present at the neuronal membrane, their presence is differentially regulated.

Genistein and daidzein induced apoA-1 transactivation in hepG2 cells expressing oestrogen receptor-α

Studies have shown that soya consumption has been associated with low incidence of CVD. Because the chemical structures of soya isoflavones are similar to oestrogen, the beneficial outcome may be attributed to the oestrogenicity of these compounds. In this study, effect of the soya isoflavone genistein on the mRNA expression of apoA-1 in the human hepatoma HepG2 cell was investigated. Without oestrogen receptor (ER) α transfection, soya isoflavones in the physiological range had no effect on the apoA-1 transcription. Once ERα was ectopically expressed in these cells, soya isoflavone dramatically increased the apoA-1 mRNA abundance quantified by real-time PCR.ApoA-1-reporter assays with plasmid constructed from the 5′-flanking segment upstream to the coding region revealed that the transactivation of theapoA-1promoter was induced by the soya isoflavone in HepG2 cells expressing ERα. This induction was reduced by the anti-oestrogen ICI 182780, but not the inhibitors of protein kinase (PK) C, PKA, or mitogen-activated PK. Based on the previously identified response elements on the promoter, a series of truncated promoter reporter plasmids were then constructed. An induction profile of genistein was built and insulin response core element at − 411 to − 404 appeared to be a potential site of interaction. This study illustrated that soya isoflavones at physiological concentrations could up regulate apoA-1 mRNA expression in ERα-transfected HepG2 cells.

Benzothiepin-derived molecular scaffolds for estrogen receptor modulators: synthesis and antagonistic effects in breast cancer cells

A series of novel benzothiepin-derived compounds are described as potent selective modulators of the human estrogen receptor (SERMs). The objective of the study is to evaluate the antiproliferative effects of the compounds on human MCF-7 breast tumor cells. These heterocyclic compounds contain the traditional triarylethylene arrangement exemplified by tamoxifen, conformationally restrained through the incorporation of the benzothiepin ring system. The compounds demonstrated potency at nanomolar concentrations in antiproliferative assays against an MCF-7 human breast cancer cell line with low cytotoxicity. The compounds exhibited low nanomolar binding affinity for the estrogen receptor (ER) with some specificity for ERbeta, and also demonstrate potent antiestrogenic properties in the human uterine Ishikawa cell line. The effect of a number of functional group substitutions on the ER binding properties of the benzothiepin molecular scaffold is explored through a brief computational structure-activity relationship investigation with molecular simulation.

ER-beta expression in large bowel adenomas: implications in colon carcinogenesis

BACKGROUND

A pivotal role of oestrogen receptor-beta has been suggested in colon carcinogenesis in humans. However, few data are available on oestrogen receptor-beta in colorectal pre-cancerous lesions.

AIM

In the present study, we evaluated oestrogen receptor-beta expression and its possible correlation with proliferative activity and apoptosis in colorectal adenomas and normal colon tissue.

PATIENTS/METHODS

Adenomatous tissue from 25 patients with colonic polyps, and normal tissue from 25 controls were used. Oestrogen receptor-beta expression, colonocyte proliferation (expressed as PCNA positivity) and apoptosis were evaluated.

RESULTS

In adenomatous tissue, a significant reduction of oestrogen receptor-beta was observed compared to normal mucosa (10.1+/-5.5% vs. 44.2+/-13.7; p<0.03), while the expression of oestrogen receptor-alpha remained unvaried. Cell proliferative activity significantly increased in adenomatous tissue compared to normal mucosa (59.3+/-7.1 vs. 18.5+/-8.8; p<0.0001), doubling the PCNA/apoptosis ratio. An inverse correlation was found between oestrogen receptor-beta and PCNA expression in adenomas (r=-0.81), a datum confirmed by confocal microscopy evaluation.

CONCLUSIONS

Our data demonstrate, for the first time, a significant reduction of oestrogen receptor-beta expression already in the pre-cancerous phase of colon carcinogenesis. This suggests a role of selective oestrogen receptor-beta agonists in the prevention of colorectal cancer.

Identification of estrogen receptor alpha gene polymorphisms by SSCP and its effect on reproductive traits in Japanese flounder (Paralichthys olivaceus)

Estrogen receptor (ERalpha) modifies the expression of genes involved in cell growth, proliferation and differentiation through binding to estrogen response elements (EREs) located in a number of gene promoters, so the ERalpha gene is considered as an important factor affecting reproductive endocrinology in Japanese flounder (Paralichthys olivaceus). In this study, twelve single nucleotide polymorphisms (SNPs) within eight CDS exons and 1 kb of 3'-UTR of the ERalpha gene were tested to association with four reproductive traits in a population of 119 Japanese flounder individuals with polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP). The association analysis of SNPs within Japanese flounder ERalpha gene with the reproductive traits was carried out using General Linear Model (GLM) estimation. Results indicated that two SNPs in the exon4 of ERalpha gene, P1 (A803G and C864T), were significantly associated with hepatosomatic index (HSI) (P<0.05) in female Japanese flounder. Other ten SNPs in 3'-UTR associated to serum 17beta-estradiol (E(2)) and HSI showed that P2 (A1982T) was significantly associated with E(2) (P<0.01) and P3 (A2149G, 2181TTACAAG2182 insertion or deletion, T2324G, A2359G and G2391A) was significantly associated with HSI (P<0.05) in female Japanese flounder. However, P2 (A1982T) and P4 (G2256T, T2294C, T2309G and A2333T) had significant effects on E(2) (P<0.05 and P<0.01, respectively) in male Japanese flounder. In addition, there were significant associations between diplotype D1 based on fourteen SNPs and reproductive traits. The genetic effects for HSI (female) or E(2) (male) of diplotype D1 were significantly higher than those of other eight diplotypes (P<0.05), respectively. Our findings implied that P1 of ERalpha gene affecting the reproductive traits could be a potential QTN (quantitative trait nucleotide) which would be useful genetic marker in the selection of some reproductive traits for its in Japanese flounder.

Decursin and decursinol angelate inhibit estrogen-stimulated and estrogen-independent growth and survival of breast cancer cells

Introduction

Estrogen and estrogen receptor (ER)-mediated signaling are crucial for the etiology and progression of human breast cancer. Attenuating ER activities by natural products is a promising strategy to decrease breast cancer risk. We recently discovered that the pyranocoumarin compound decursin and its isomer decursinol angelate (DA) have potent novel antiandrogen receptor signaling activities. Because the ER and the androgen receptor belong to the steroid receptor superfamily, we examined whether these compounds affected ER expression and signaling in breast cancer cells.

Methods

We treated estrogen-dependent MCF-7 and estrogen-independent MDA MB-231 human breast cancer cells with decursin and DA, and examined cell growth, apoptosis, and ERα and ERβ expression in both cell lines – and, in particular, estrogen-stimulated signaling in the MCF-7 cells. We compared these compounds with decursinol to determine their structure-activity relationship.

Results

Decursin and DA exerted growth inhibitory effects on MCF-7 cells through G₁ arrest and caspase-mediated apoptosis. These compounds decreased ERα in MCF-7 cells at both mRNA and protein levels, and suppressed estrogen-stimulated genes. Decursin and the pure antiestrogen Faslodex™ exerted an additive growth inhibitory effect on MCF-7 cells. In MDA MB-231 cells, these compounds induced cell-cycle arrests in the G₁ and G₂ phases as well as inducing apoptosis, accompanied by an increased expression of ERβ. In contrast, decursinol, which lacks the side chain of decursin and DA, did not have these cellular and molecular activities at comparable concentrations.

Conclusion

The side chain of decursin and DA is crucial for their anti-ER signaling and breast cancer growth inhibitory activities. These data provide mechanistic rationales for validating the chemopreventive and therapeutic efficacy of decursin and its derivatives in preclinical animal models of breast cancer.

Rapid signaling mechanisms of estrogens in the developing cerebellum

The steroid hormone 17beta-estradiol regulates the normal function and development of the mammalian nervous system. Many of estradiol's effects are mediated via the nuclear hormone estrogen receptors ERalpha and ERbeta. In addition to regulating estrogen-responsive gene expression, estradiol also acts in an immediate and cell-specific fashion to regulate various intracellular signal transduction pathways. The goal of this review is to develop a contextual framework to understand the generalized function of estrogen during development of brain regions not known to be sexually specialized. However, it is first important to build this framework on the more well-developed foundation of estrogen's gonad-driven sex-specific actions. As a result, a discussion of known and proposed mechanisms of estrogen actions in reproductive and other tissues will be presented. Building upon this information, a review of our research group's recent in vitro and in vivo studies that have focused on elucidating the mechanisms of estrogen actions in neurons of the non-sexually specialized cerebellum will be presented. While the full spectrum of estrogen action during normal cerebellar development remains unresolved, results of recent studies have revealed a pathologic role for estrogen and estrogen receptors in medulloblastoma, common pediatric brain tumors that arise from cerebellar granule cell-like precursors. The potential use of anti-estrogen signaling agents as adjuvant therapy for medulloblastoma is proposed based on those finding.

Screening of synthetic and plant-derived compounds for (anti)estrogenic and (anti)androgenic activities

Recently we constructed yeast cells that either express the human estrogen receptor alpha or the human androgen receptor in combination with a consensus ERE or ARE repeat in the promoter region of a green fluorescent protein (yEGFP) read-out system. These bioassays were proven to be highly specific for their cognate agonistic compounds. In this study the value of these yeast bioassays was assessed for analysis of compounds with antagonistic properties. Several pure antagonists, selective estrogen receptor modulators (SERMs) and plant-derived compounds were tested. The pure antiestrogens ICI 182,780 and RU 58668 were also classified as pure ER antagonists in the yeast estrogen bioassay and the pure antiandrogen flutamide was also a pure AR antagonist in the yeast androgen bioassay. The plant-derived compounds flavone and guggulsterone displayed both antiestrogenic and antiandrogenic activities, while 3,3'-diindolylmethane (DIM) and equol combined an estrogenic mode of action with an antiandrogenic activity. Indol-3-carbinol (I3C) only showed an antiandrogenic activity. Coumestrol, genistein, naringenin and 8-prenylnaringenin were estrogenic and acted additively, while the plant sterols failed to show any effect. Although hormonally inactive, in vitro and in vivo metabolism of the aforementioned plant sterols may still lead to the formation of active metabolites in other test systems.

Nanoparticles loaded with ferrocenyl tamoxifen derivatives for breast cancer treatment

For the first time, two organometallic triphenylethylene compounds (Fc-diOH and DFO), with strong antiproliferative activity in breast cancer cells, but insoluble in biological fluids, were incorporated in two types of stealth nanoparticles (NP): PEG/PLA nanospheres (NS) and nanocapsules (NC). Their physicochemical parameters were measured (size, zeta potential, encapsulation and loading efficiency), and their biological activity was assessed. In vitro drug release after high dilution of loaded NPs was measured by estradiol binding competition in MELN cells. The influence of the encapsulated drugs on the cell cycle and apoptosis was studied by flow cytometry analyses. Notwithstanding potential drug adsorption at the NP surface, Fc-diOH and DFO were incorporated efficiently in NC and NS, which slowly released both compounds. They arrested the cell cycle in the S-phase and induced apoptosis, whose activity is increased by loaded NS. A decrease in their antiproliferative activity by the antioxidant alpha-tocopherol indicated that reactive oxygen species (ROS) may be involved. Therefore, nanosystems, containing for the first time a high load of anticancer organometallic triphenylethylenes, have been developed. Their small size and delayed drug release, combined with their enhanced apoptotic potential, are compatible with an increased persistence in the blood and a promising antitumour activity.

Role of estrogens and their receptors in adhesion and invasiveness of breast cancer cells

Estrogen receptors (ERs) are overexpressed in human breast cancers (BCs) and associated with differentiated tumors and with a more favorable prognosis. Paradoxically, ERs mediate the mitogenic action of estrogens in human BC cells and the efficacy of antiestrogens in adjuvant therapy of primary tumors. The exact mechanism underlying the ER protection against cancer progression to metastasis remains to be investigated. Herein, we show that ERs decrease invasiveness of BC cells. Detailed studies revealed that the unliganded and the E2-activated ERs decrease cancer cell invasion in vitro through two distinct mechanisms. In the presence of ligand, ERalpha inhibits invasion through a mechanism requiring the functional ERalpha domains involved in the transcriptional activation of target genes. Moreover, using different approaches, we found that cell-cell contacts were markedly increased by 17beta-estradiol (E2) treatment and decreased by the pure antiestrogen, ICI182,780. This cell-cell adhesion was associated with an increase of the major intercellular junctions, desmosomes. Conversely, in the absence of ligand, ERalpha also inhibits invasion through a distinct mechanism involving protein-protein interaction with the region of the first zinc finger of ERalpha. The relationship of these data with clinical studies and their potential therapeutic consequences will be discussed.